The present invention relates generally to devices for engraving text or images onto a workpiece by removing portions of the workpiece corresponding to the engraved text or images. More particularly, the present invention relates to a laser assembly adapted to retrofit industrial mechanical engravers to convert the mechanical engraver to a laser engraver.
Generally, the present invention provides a laser assembly, which may employ any type of laser suitable for the material to be engraved, e.g., YAG, CO.sub.2 or excimer laser. Mounting bracketry mounts the laser and associated focusing optics onto the mechanical engraver. Additional laser optics, such as mirrors and lenses, may also be employed with the laser to focus an engraving beam onto the material to be engraved. In conjunction with the laser, various electronics are supplied, such as a power supply, a pulse generator, and conducting wiring, which actuate the laser. The primary control component is a delay circuit which minimizes or adjustably suppresses the first laser pulse when an initiation signal is received from the controller. The first laser pulse typically emits too much energy which results in uneven marking depth and width at the point of initial marking. Neither conventional laser nor mechanical engraving systems compensate for the delay between the time that the start signal is received and movement of the engraver is initiated.
An example of an embodiment of the present invention is a laser system consisting of a mirror connected to the spindle, collet or chuck assembly of the mechanical engraver, and used in place of the engraving tool or bit. The mirror may consist of a single mirror and lens assembly with the laser mounted to the existing gantry assembly and movable with the gantry. The spindle, collet or chuck assembly moves on the gantry to emit a laser, which is directed, either by the optics onto the workpiece. Alternatively, the optics ma be mounted on the spindle, collet or chuck assembly and be moveable, with the laser mounted stationary, but in the optical path of the moveable mirror. Alternatively, a two-axis optical system may be utilized with a stationary mounted laser assembly. The focusing optics in all of these configurations may be either before or after the mirror assembly and the gantry is capable of either x, y axis motion or only x or only y axis motion with a moveable workpiece. For purposes of clarity, reference to x, y or z-axes refers to movement relative to a workpiece.
The invention provides a retrofit for existing mechanical engravers and substitutes the laser assembly for the chuck, collet and/or spindle assembly of the mechanical engraver. Existing mechanical engraver control processing is be utilized for movement of the engraver.
Jones, et al. U.S. Pat. No. 4,564,736, issued in 1986, disclose a hand-held laser marking tool which is coupled to a laser system via a quartz fiber-optic cable to permit use of a solid state pulsed laser with a hand-held stylus for manual engraving and/or marking of a workpiece. This patent is illustrative of a portable laser system in which the moveable laser tool is connected to a stationary laser system.
Garnier, et al., U.S. Pat. No. 4,985,780, issued in 1991, disclose a laser engraving device in which an electronic controller controls two carriages for movement of a laser beam delivery system in both the x and y directions. The carriage system employs two servo motors which are controlled by the controller to move the laser beam delivery system. The laser beam delivery system includes a series of mirrors. A first mirror receives the laser beam from the laser source and orients the beam perpendicular to the direction of output. A second mirror receives the reflected beam and directs it in a direction parallel to the direction of the initial laser beam output, but in a direction opposite from that of the original output direction. A third mirror reflects the received laser beam in a direction perpendicular to the incident received beam and a fourth mirror receives the reflected beam and directs it perpendicular into a focusing lens. The focusing lens focuses the beam onto a workpiece to be engraved. The laser beam delivery source is a stationary unit and the mirror and focusing optics are moveable on the x, y carriages. This patent is cited as an example of a moveable engraving beam which is carried on an x, y gantry carriage system to mark a workpiece. It is analogous to the construction of a mechanical engraver as it would be adapted for laser engraving purposes. There is no disclosure in this patent, however, that the system of this patent could be retrofit to a mechanical engraver.
Macken, U.S. Pat. No. 4,480,169, issued in 1984, discloses a non-contact laser engraving device. The device consists generally of a workpiece and a reflecting mirror which carries a design image and acts as a pattern for the laser beam to reproduce the design image onto the workpiece. Both the reflecting mirror and the workpiece are carried on a moveable tray. The laser beam is focused onto a first mirror which reflects the laser beam onto the pattern mirror and the patterned mirror reflects the laser beam from the mirror surface onto a second reflecting mirror. A lens focuses the reflected beam onto a third reflecting mirror, which reflects the beam onto the workpiece to reproduce the stencil image. This patent describes a laser engraver which employs stationary optics, a stationary laser beam with a moveable workpiece for non-contact laser engraving.
Heller, et al. U.S. Pat. No. 3,588,439, issued in 1971, disclose a pulsed laser engraving system which permits the surface of a workpiece to be engraved across its entire surface with coherent light which passes through a predetermined masking pattern. The patent discloses a stationary workpiece and a stationary optics system for engraving the workpiece.
Nakano, U.S. Pat. No. 4,758,848, issued in 1988, discloses a laser engraving apparatus for marking a pattern with a laser beam. The laser beam which is not utilized for the pattern marking is fed back to a previous stage to increase the energy efficiency of the laser beam. The apparatus consists of a laser oscillator and a coupler attached to the laser oscillator. A collimator is connected to the laser oscillator through an optical fiber connected to the coupler. A polarizer is positioned in the path of the laser beam which is emitted from the collimator and an expander, composed of a concave lens and a convex lens, is positioned in the path of the laser beam emitted from the polarizer. A liquid crystal display is interposed in the path of the laser beam from the lenses and functions as a light valve or mask to generate the pattern to be marked on the article. A beam analyzer is positioned at a predetermined angle to the laser beam path from the liquid crystal device and a lens is provided for focusing the laser beam passed through the analyzer to mark the pattern on the article. This apparatus is directed generally to an apparatus to mark a pattern based upon the mask generated by the LCD device and to provide an increase in energy efficiency of laser usage for the laser energy not utilized for marking purposes.
Sorkoram, U.S. Pat. No. 4,851,061, issued in 1989, discloses a laser device for cutting thermoplastic materials. The device consists generally of a controller which operates the laser cutting tool to generate a pattern which is cut from a thermoplastic workpiece. The pattern to be created in the thermoplastic material is derived from programmed coordinates which are stored in the controller. The laser cutting tool responds to the controller by being displaced on a cutting table in both the x and y axis. While the manner in which the cutting tool is moved is not specifically disclosed, the patent to Garnier, et al. discloses a type of apparatus which can be used for x, y axis movement with a laser cutting head. This patent is primarily directed to an underlying cutting table support consisting of a plurality of honeycombed chambers through which the laser may be exhausted via a vacuum source. This patent is illustrative of a type of laser cutting head which is known in the art.
Finally, patents to Johnson, et al., U.S. Pat. No. 2,810,960, issued in 1957, Sicking, et al., U.S. Pat. No. 3,353,273, issued in 1967, and Sovar, et al., U.S. Pat. No. 3,339,279, also issued in 1967, illustrate conventional mechanical engravers as are known in the art. The mechanical engravers each employ a stylus which is held in a collet or chuck and connected to a vacuum source for removing shavings from the engraved work.
The current state of the art falls short of providing a laser retrofit assembly to convert mechanical engravers to laser engravers without changing control processing of the mechanical engraver. While it is known to use a hand-held portable laser stylus is known in the art as represented by the Jones, et al. patent, wherein the laser is hooked to a stationary laser oscillator via optical cables, and use a laser stylus mounted on an x, y axis gantry as shown by Garnier, et al, there are no current systems which enjoy the features and advantages of the present invention.